1. Field of Invention
The present invention relates to a component for a liquid crystal display, and more particularly to a hard-screen polarizing plate component and a liquid crystal screen applying the polarizing plate.
2. Description of Related Arts
The polarizer, which is an optical thin-film composited by multilayers of polymer materials and having a function of generating polarized light, is one of the most important components in Liquid Crystal Displays (LCD). As shown in FIG. 1 of the drawings, polarizers are adhered to both surfaces of a liquid crystal cell 4. The polarizers are respectively called an upper polarizer 01 (or a transmission film) and a lower polarizer 02 (or a reflector film), and has a function to polarize back lights. By changing an electrical signal of a liquid crystal layer in the liquid crystal cell of the liquid crystal display, liquid crystal molecules of the liquid crystal layer generate torsional arrangement and form an optical channel having a certain torsion angle. Therefore, when polarized lights pass through the optical channel, passing quantity and blocked quantity thereof are controlled, so as to display a brightly colorful image.
The common-used upper polarizer currently has a sandwich structure. As shown in FIG. 1 of the drawings, the upper polarizer consists of two layers of protective films 04 and 05, and a polarizing film 03 provided therebetween, wherein the polarizing film 03 is manufactured by processing staining and stretching to polyvinyl alcohol materials. Properties of the polarizing film 03 determine polarized property and transmittance of the polarizing film 03, and influence hue and optical durability thereof as well. The polarizing film 03 made of polyvinyl alcohol is easy to lose polarized property due to water absorbing and color fading. Thus, the protective films 04 and 05 having good optical homogeneity and transparency are required to be provided on both surfaces of the polarizing film 03 respectively, so as to isolate from water and air for protecting the polarizing film. The protective films 04 and 05 are usually made of a cellulose triacetate membrane (TAC). The ultra-violet cut type polarizer or anti-glare type polarizer can be manufactured by applying cellulose triacetate membrane having functions of ultra-violet cut or anti-glare. And the liquid crystal display device is formed by adhering polarizers to glass surfaces 41 of the liquid crystal cell 4.
Since various liquid crystal screens are more and more widely applied, especially the large-screen LCD TV, technological, visual and cost requirements of people for the liquid crystal screen is higher and higher. For example, the structure thereof is required to be ultra thin and frameless, bright and gorgeous screen in appearance, and in practical aspects, the liquid crystal screen is required to have moisture resistance and impact resistance, and has optical property of improving contrast and reducing light-flux loss. With applications of three-dimensional technologies in the liquid crystal display device, the liquid crystal screens are further required to be capable of showing high-level gradation effects of an image. And on the other hand, people require manufacturing costs of the liquid crystal screen to be lower and lower. As important components in the liquid crystal screen, the polarizers, and especially the upper polarizer is directly related to the corresponding properties of the liquid crystal screen. However, the polarizers in prior arts can not fully meet technical requirements mentioned above, which specifically shows as following.
1. Taking a polarizer with a cellulose triacetate membrane as a film of protective layer as an example, since the cellulose triacetate membrane still has some water vapor permeability, wherein permeability thereof is approximately 300 g/m2/day, protective capability thereof is slightly insufficient under conditions of high temperature and high humidity.
2. After a hard coat layer is added, scratching resistance of a surface of the protective layer is capable of reaching a maximum value of 3H (surface hardness) in theory. However, since the polarizer is made of flexible materials and thickness thereof is approximately 300 μm, when the polarizer is adhered directly to a fragile glass surface of the liquid crystal cell, the polarizer does not have sufficient rigidity to meet high requirements for scratching resistance.
3. Since the polarizer is made of flexible materials and is not capable of protecting the liquid crystal cell, the liquid crystal cell is easily damaged when the liquid crystal screen is impacted by external force or impressed by large pressure.
4. As shown in FIG. 2 of the drawings, in order to prevent external light interference, a light emitting surface of a protective film 04 is usually treated by a rough surface, in such a manner that an effect of anti-glare is achieved. However, treating of the rough surface has a dual character, i.e., although the treating of the rough surface achieves an object of scattering external obtrusive lights, the rough surface has a scattering effect on lights emitted by the liquid crystal cell as well, which reduces a property of contrast of the liquid crystal screen.
Currently, hard screen techniques having improvements on appearance structures and security of the display comes into application, which has achieved characteristics such as frameless surface, gorgeous and impact resistance of the display. As shown in FIG. 3 of the drawings, a hard screen 09 as shown is formed by adding a high transparency hard material 06, such as organic glass (acrylic plate) and printed black frame glass. Two surfaces of the high transparency hard material 06 need to be respectively adhered with a protective film 07. The hard screen 09 which is relatively independently added does not relate to basic structure of the liquid crystal screen formed by polarizer. Due to gaps between the hard screen 09 and the liquid crystal screen, polarized lights emitted by the liquid crystal screen generates secondary refraction and internal reflection, so that quality of images displayed thereof is directly influenced. As an improvement, light-conductive resin 08 is filled between the hard screen 09 and the polarizer 01, which solves a problem of secondary refraction by application of the hard screen, but increases difficulty of manufacturing process and costs thereof as well.